Type 1 diabetes occurs in individuals who are genetically susceptible. However, even in identical twins, diabetes-may occur in one and not in the other. The present invention relies upon the discovery of an environmental trigger for Type 1 diabetes which operates very early in life.
The evidence that this environmental trigger is to be found in cows milk is based on epidemiological (Leslie et al, 1994), ecological (Virtanen et al, 1993) and animal experimental evidence (Elliott & Martin, 1984 and Elliott 1992). The diabetogenic factor of the milk appears to be in the casein fraction (Elliott et al, 1992), at least in the non-obese diabetic (NOD) mouse. Whey protein does not appear to, contain any diabetogenic component (Elliott et al, 1992). It has been suggested that bovine serum albumin (BSA), a protein found in the whey fraction of cows milk is the diabetogenic component of cows milk (Sheard, 1993). However, a review of the evidence supporting this theory does not indicate that BSA was ever tested for diabetogenic activity in the absence of β-casein.
International PCT Application WO95/10537 discloses a method of producing denatured bovine serum albumin milk products. It is stated that the consumption of denatured BSA milk products tends to reduce the likelihood of a person acquiring type 1 diabetes. However, there is no evidence presented of any trials where either human or animal subjects were fed milk or milk products with denatured BSA. It relies upon the theory mentioned above that BSA is the diabetogenic component of cows milk (Sheard, 1993). In European Patent Application 629,350 there is described a method of hydrolysing cows milk protein to produce a hydrolysates substantially free of allergenic proteins. The hydrolysate also is suggested to be useful in the prophylaxis and treatment of type 1 diabetes melitis in children susceptible to such disease. In the description on page 6 of that specification it is suggested that BSA may be a trigger to the immune system. However, there are no examples in the patent specification and no reference to any papers showing any direct evidence of this suggestion.
In South African patent specifications 61/1804 laid open on 28 Jun. 1961, 61/2068 laid open on 20 Sep. 1961 and 62/600 laid open on 4 Jul. 1962 there are described compositions alleged to be cures for diabetes. There are no examples, of any trials in support of these assertions. The compositions consist of casein as a base and fruit and leaves of South Africa plants. It is inferable from the description that the active ingredient is the plant material and there is no mention that casein has any role in causing or curing diabetes.
We have now tested the A1 and A2 variants of β-casein and a whey protein on NOD mice and found that the A1 variant does have diabetogenic activity while the A2 variant and whey protein do not show diabetogenic activity.
It is an object of one aspect of the invention to use this finding to go some way to selecting milk and milk products which do not contain a diabetogenic factor in such milk or milk product or at least to offer the public a useful choice.
It is an object of another aspect of this invention to go some way towards selectively breeding cows and bulls whose offspring produce milk which is not diabetogenic or which at least offers the public a useful choice.